Metaphosphate glass



United States Patent O 3,328,131 METAPHOSPHATE GLASS Robert A. Weidel, Webster, N.Y., assignor to Bausch & Lomb Incorporated, Rochester, N.Y., a corporation of New York No Drawing. Filed Mar. 28, 1963, Ser. No. 268,548 5 Claims. (Cl. 10647) This invention relates to a novel glass composition and more particularly to a glass composition having a relatively low index of refraction and a relatively low dispersion which is a relatively high 1 value.

Phosphate glasses have been widely accepted for various commercial applications, see for example the patent of Gerald E. Blair 2,999,819. The Blair patent discloses the use of an aluminum metaphosphate, magnesium metaphosphate, lithium metaphosphate glass having silver metaphosphate incorporated therein for use as a dosimeter. Another example of such glasses is shown in the patent to W. A. Well 2,486,812 wherein an aluminum phosphate material is used as a glassy binder for an electrical insulating composition. Phosphate glasses have also been used for optical glasses. For example, the patent to Izumitani et a1. 2,919,201 discloses an optical glass including approximately 50-64 weight percent aluminum metaphosphate.

Phosphate glasses with anomalous partial dispersions have been disclosed in the patent of G. Weissenberg et 2.1. 2,996,390. Glasses of this type include at least 50% by weight of a metaphosphate of an alkaline earth metal and up to 50% by weight of compounds selected from the group consisting of the alkali and alkaline earth metals. Lead oxide, or lead phosphate and boric acid may also be added to the mix.

Optical glasses are commonly selected in View of their refractive index and 1 value. The index of refraction is usually given for the sodium line and is designated by 11;; while the 1 value is defined as n 1 divided by n n wherein n and n refer to the refractive indices measured at 4861 A. and 6563 A. respectively. For certain applications however, it is highly desirable to have a glass having a particular index of refraction, and 1/ value, and yet one which has unusual partial dispersion ratios. The partial dispersion ratios in the visible portion of the spectrum is usually measured by the quantity P, =n,n Ordinarily A is taken as the F line in the spectrum and the partial dispersion is then a measure of the ability of the glass to correct for secondary color.

In most cases glasses having a particular index 11 and 1 value are characterized by a substantially linear relationship between P and 11. One notable exception to this rule is the family of so-called short flint glasses which are further characterized by a substantially lower P value than the ordinary glasses having similar 11 values.

The P value of the glasses according to the present invention have been found to differ from ordinary glasses in having a substantially higher P value than common glasses with similar 11 values. These glasses having substantially higher P values are particularly desirable for use in color corrected lens systems. For example, the optical elements made from the glasses according to the present invention may be combined with elements made from thte short flint glasses in order to match the P values and thereby correct for secondary color.

The partial indices of the glasses disclosed herein depart from the straight line function to a somewhat lesser degree than those glasses disclosed and claimed in my copending application entitled Optical Glass filed Mar. 28, 1963, SN. 268,547, now US. Patent No. 3,281,- 253, and assigned to the same assignee as the present invention.

3,328,181 Patented June 27, 1967 Compositions according to the present invention can be manufactured in relatively large melts and do not have a strong tendency for devitrification. Furthermore these glasses may be manufactured into optical elements of the usual sizes and shapes and are particularly desirable for secondary color correction in lens systems.

Briefly, the glass compositions disclosed herein consist essentially of an aluminum metaphosphate, alkali metaphosphate, and alkaline earth metaphosphate. The aforementioned ingredients are present within the range of 33.150 weight percent, 16-25 weight percent and 16-25 weight percent respectively. The glasses according to the presently preferred embodiments also include either B 0 or TiO in the range of 1-10 weight percent and may contain various other glass modifiers in an amount less than 11.5 Weight percent.

The metaphosphates are more desirable than other phosphorous materials such as phosphorous pentoxide since they are more stable and therefore improve the reproducibility of the glasses, simplify the handling techniques and facilitate melting the compositions.

It should also be understood that various oxides or other conventional glass modifiers may be added to the examples disclosed herein. The quantities of such oxides and modifiers is governed by conventional glass techniques, however, for a first approximation they would not exceed 10 weight percent. These oxides may be added to the batch as the oxides themselves and any desired material which would decompose or react in the melt to produce the specified oxides. For example, the corresponding carbonates or hydrates may be used. Examples of these materials include barium carbonate, zinc oxide, potassium carbonate, sodium carbonate, zirconium dioxide, calcium carbonate, magnesium carbonate, strontium carbonate, lead oxide, borax, lithium oxide, rubidium oxide, cesium oxide, cadmium oxide, aluminum oxide, lanthanum oxide, silica, germanium dioxide, niobium oxide, tantalum oxide, bismuth oxide, tellurium oxide and others.

The following examples set forth several operative embodiments of the invention and are not to be construed as limiting the scope of the invention. The examples are given in weight percent batch basis:

A B C D E F G AI(PO3)3 45. 5 44. 3 43. 3 42. 3 41. 3 B3.(PO3)z 22.7 22.2 21.6 21.1 20.6 LiPO 22. 7 2 2 6 21. 1 20. 6 1 9 7 8. 5 8. 3

H I J K L M N Al(POa)3. 48. 8 47. 6 41. 6 41. 6 41 6 47. 6 47. 6 Ba(PO3)z 20.8 20.8 5.2 5.2 Mg(P03)2. 24.4 23.8 20.8 18.6 18.6 K(PO3) 24.4 23.3 20.8 20.8 20.8 23.8 23.8 B 03 2.4 4.8 16.8 16.8 16.8 4.8 4.8 12.. 1. 513 1. 513 1. 536 1. 535 1. 515 1. 517 l. 516 u 69.8 70. 2 70- 5 70.9 70.8 70. 2 70 O P Q R S T U AI(PO3)3 48.8 40. 6 39. 6 37. 7 36. 0 34. 4 33.1 -.4 20.3 19.8 18.9 18.0 17.3 11.5 .4 20. 3 19. 8 18. 9 18.0 17. 3 16. 5 16. 3 15. 9 15. 1 14. 5 13. 8 13. 3 2. 5 4. 9 9. 4 13. 5 17. 2 20. 6 1. 533 l. 545 1. 573 1. 599 1. 624 1. 646 59. 1 51.6 41.6 36.0 32.3 29.7

Examples H and I represent the presently preferred embodiments of the invention.

The optical characteristics of selected examples including the partial indices measured at various wavelengths The conditions and controls for carrying out the melting, annealing, and cooling steps are subject to wide variation. For example, in some cases a batch of raw ingredients may be melted in a refractory pot, or a platinum lined vessel. Similarly, temperatures, times and conditions vary according to the amount of glass being formed, therefore the temperature and melting conditions recited hereinafter are given by way of illustration and are not intended to limit the scope of the appended claims.

For example, the ingredients in the powdered form are mixed together and placed in a platinum clucible. The crucible containing the mixture is placed in an electric resistance furnace and the ingredients are melted therein at a temperature of approximately 12001300 C. Relatively small melts were made in this manner and were held at this temperature for approximately 3-4 hours. Larger melts could also be made at this same temperature, however, with larger melts it is desirable to stir the glass according to conventional glass making techniques for approximately 4 hours. The melts were cast at approximately 8001200 C. on a plate having a temperature of approximately 100-300 C. All types of the glass disclosed herein were annealed at approximately 300- 500 C.

Such matters as contained in the text Properties of Glass by G. W. Morey, Modern Ophthalmic Lenses and Optical Glass by Theo. E. Obrig (1935) and The Manufacture of Optical Glass and of Optical Systems, Ordnance Department, Document 2037, Government Printing 4 Office 1924 set forth additional details about glass manufacturing. Such details are considered to comprise the background information about the manufacture of optical glasses and are considered to be conventional.

What is claimed is:

1. A glass composition consisting essentially of 41-50 weight percent aluminum metaphosphate, 20-25 Weight percent alkali metal metaphosphate, 1825 weight percent alkaline earth metaphosphate and 2-17% weight percent B 0 2. A glass composition consisting essentially of 48.8 weight percent aluminum metaphosphate, 24.4 weight percent magnesium metaphosphate, 24.4 weight percent potassium metaphosphate and 2.4 weight percent B 0 3. A glass composition consisting essentially of 47.6 weight percent aluminum metaphosphate, 23.8 weight percent magnesium metaphosphate, 23.8 weight percent potassium metaphosphate and 4.8 weight percent B 0 4. A glass composition consisting essentially of 48.8 weight percent aluminum metaphosphate, 24.4 weight percent magnesium metaphosphate, 24.4 weight percent potassium metaphosphate and 2.4 weight percent titanium dioxide.

5. A glass composition consisting essentially of 33-41 weight percent aluminum metaphosphate, 16-21 weight percent magnesium metaphosphate, 16-21 weight percent potassium metaphosphate, 0-163 weight percent B 0 and 2.4-20.6 weight percent titanium dioxide wherein the total weight percent range of B 0 and titanium dioxide is between 2.4-34.

References Cited UNITED STATES PATENTS 2,294,844 9/ 194-2 Gelstharp 106-47 2,577,627 12/1951 Pincus 10647 FOREIGN PATENTS 1,339,024 8/ 1963 France.

OTHER REFERENCES Bromer et al., German application 1,089,935, printed Sept. 29, 1960 (K1 32b1), 3 pages spec.

Jahn, German application 1,089,934, printed Sept. 29, 1960 (K1 32bl), 3 pages spec.

HELEN M. MCCARTHY, Primary Examiner. 

1. A GLASS COMPOSITION CONSISTING ESSENTIALLY OF 41-50 WEIGHT PERCENT ALUMINUM METAPHOSPHATE, 20-25 WEIGHT PERCENT ALKALI METAL METAPHOSPHATE, 18-25 WEIGHT PERCENT ALKALINE EARTH METAPHOSPHATE AND 2-17% WEIGHT PERCENT B2O3.
 5. A GLASS COMPOSITION CONSISTING ESSENTIALLY OF 33-41 WEIGHT PERCENT ALUMINUM METAPHOSPHATE, 16-21 WEIGHT PERCENT POTASSIUM METAPHOSPHATE, 0-16.3 WEIGHT PERCENT B2O3 AND 2.4-20.6 WEIGHT PERCENT TITANIUM DIOXIDE WHEREIN THE TOTAL WEIGHT PERCENT RANGE OF B2O3 AND TITANIUM DIOXIDE IS BETWEEN 2.4-34. 